Transistorized ignition system



June 14, 1960 G. M. FORD 2,941,119

TRANSISTORIZED IGNITION SYSTEM Filed May 6, 1958 IN VEN TOR.

A TTORNEY.

United States Patent Q TRANSISTURIZED rGNrrIoN SYSTEM Gerald M. Ford, Kokomo, Ind, assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed Mar. s, 1958, 821'. No. 719,661

2 Claims. c1. sis-a2 This invention relates to an improved ignition system for internal combustion engines. With the conventional ignition coil-breaker type of ignition system currently in use, there is a definite maximum voltage obtainable from thesecondary winding with a storage battery source connected in the primary. It is desirable to provide a high secondary voltage to apply to the spark plugs in order to obtain satisfactory ignition of the combustible mixture in the cylinderand also to reduce wear on the electrodes of the spark plugs. In the past, it has been found that a iurnratio of 100-1 in the ignition transformer is the optimum. At any higher turn ratio, the distributed capacity of the coil is a limiting factor and nothing is gained from a practical standpoint. This has limited the voltages used with conventional coils and breaker systems to some 17,000 volts. It would be advantageous to the ignition system to be able to obtain thirty thousand volts or perhaps more.

It is an object in making this invention to provide an ignition system producing higher secondary voltages and greater energy transfer than have heretofore been obtainable.

an ignition system in which uniformly high secondary voltages are available over the full range of engine speed. It is a still further object in making this invention to It is a further object in making this invention to provide provide an ignition system for an internal combustion engine utilizing transistors for controlling curent flow.

. With these and other objects in view which will become apparent as the specification proceeds, the invention will be best understood by reference to the following specification and claims and the illustration in the accompanying drawing in which:

The figure is a circuit diagram showing an ignition system embodying my invention.

Referring now more specifically to the drawing, there is shown therein a conventional automobile battery 2, one terminal of which is grounded and the other terminal connected to a movable switch arm 4 which moves between two stationary contacts 6 and 8. A second movable switch arm 10 is electrically connected to switch contact 8. The second arm 10 oscillates between two fixed contacts 12 and 14. These switches control the ignition system to operate either conventionally or to include the transistor control. The ignition system includes a breaker 16 for intermittently interrupting the primary current in either the primary winding 18 of the control transformer 20 or primary 58 of the ignition transformer 60. The breaker includes a movable switch arm 22 which is connected to ground through line 24. The arm 22 pivots around pin 26 and is engageable with a stationary contact 28 insulatedly mounted on plate 30 depending upon the angular position of a rotatable cam 32. The raised points of the cam 32 force the pivoted arm 22 outwardly to open the circuit and at low points allow the switch contacts to close. Cam 32 is of course driven by the camshaft of the engine. Contact 28 is connected through line 34 with a movable switch arm 36 of a control relay Faiented June 14, 1960 38. Control relay 38 is provided to switch from conventional ignition circuit operation to the transistorized system and has an operating coil 41 for attracting the armatures toward their lowermost position. This coil has one terminal connected to ground and the other terminal through line 43 to stationary contact 14 on the on-off switch.

Switch arm 36 oscillates between two fixed contacts 40 and 42 and is spring biased towards its upper position by spring 44. Movable switch arm 36 is ganged mechanically to move with two other arms 46 and 48 as shown by the dash line connection between the three arms. The movable switch arm 46 is connected through conductor 50 with contact 8 of the on-ofi switch. This switch arm oscillates between two fixed contacts 52 and 54. The last switch arm 48 is connected through conductor 56 to primary 58 of the ignition transformer 69. Switch arm 48 oscillates between two fixed contacts 62 and 64. Contact I 64 is connected directly to ground and contact 62 is connected through conductor 66 to stationary contact 52. Contact 54 is connected through conductor 68 with one terminal of the primary winding 18 of control transformer 20. The opposite terminal of the winding 18 is connected through conductor 70 with fixed contact 42 of relay 38. Stationary contact 40 is connected through line 72 to the remaining terminal of the primary winding 58 of the ignition transformer 60. The control transformer 20 is provided with a plurality of secondary Windings whose function it is to provide base-emitter bias for a plurality of transistors or three element semiconductor devices all of which are connectable in series between a source of power and the primary 58 of the ignition transformer.

Transistors 74, 76, 78, 80, and 82 have their adjacent collectors and emitters connected together so that they are all, in effect, connected in series. Secondary windings 84, 86, 88, 90, and 92 are connected respectively across the base-emitter electrodes of each of the transistors 74, 76, 78, 80, and 82 respectively. A tieline 94, extends between contact 54 and the emitter electrode 96 of transistor 74. Collector 98 of transistor 82 at the other end of the chain is directly connected to line 72 and thence to the primary winding 58. The high tension secondary winding 100 of the ignition transformer coil 60 has one terminal connected to ground and the other connectible to any spark plug such as 102 which is merely shown to diagrammatically illustrate any spark plug or series of spark plugs.

The two main objects of the current system are to provide as high primary current as can be obtained in order to obtain maximum energy, and also to obtain a sharp cut-off. Such a system would minimize wear on the distributor points and also minimize the effect of spark plug electrode misalignment or spark plug fouling. An added result is that this system tends to give a very uniform output over the complete driving speed range.

In describing the operation, the driver moves the switch 410 to the On position. This connects the battery to the system for operation as a transistorized control circuit. The initial result is the completion of an energizing circuit for the coil 41 of the control relay 38. This coil is energized through the following circuit: from battery 2, switch arm 4, contact 8, line 45, switch arm 10, contact 14, line 43, coil 41 to ground. The energization of this coil causes it to attract the three ganged armatures 36, 46 and 48. This completes an energizing circuit for the primary coil 18 of the control transformer 20 as follows: battery 2, switch arm 4, contact 8, line 50, armature 46, contact 54, line 68, primary winding 18, line 70, contact 42, armature 36, line 34, contact 28, arm 22, line 24, to ground. Thus, when the-contacts of the distributor close,

an energizing pulse is caused to flow through the wind- Wnww ' will -be induced in'the primary winding 58.

ing "18." This induces currents in the various secondary windings 84, 86,88, 90, and 92 to produce-a proper emittor-base bias in each of the transistors to permit a heavy current flow from the power source through the transistors tothe primary 58- and a resultant high voltageto be induced-"in" the'secondary 100. The circuit for the primary 58 f the ignition transformer is from the battery 2,

7 switch arm 4, contact 8, line 50, armature 46, line 68,

l'ine' '94, through the various transistors 74, 76, 78, 80, t

biased to conduct in a forward direction, causing heavy current to flow through theprimary 8 and induce 2i high charging voltage in the secondary 100. At this time the resistance of the transistors is low so that a maximum current can flow and a maximum amount of energy be obtained; When the points open, the bias is changed to.

effectively cut off thecurrent. However, upon a collapse of-the'field in the'ignition transformer, a high'voltage desired to have the transistors appear as high resistance for current which they provide and very little current flows. By applying'maximum energy and high voltage to the sparkplugs, the effects of burning or erosion will be minimized and by interrupting onlytlie current in the l'owvoltage primary of the control transformer 20, the wear on the breaker points will also be minimized.

Ifdesired, the ignition circuit can be operated in a conventional-manner by moving switch arm 10 from engagement withcontact 14.; This de'energ'izes relay coil 41 and it therefore allows all of its armatures 36, 46

"and-48,10 be pulled upwardly. Through an obvious cit- 'cuit, the battery is now directly'connected only through the" primary winding 58' of 'the ignition transformer and the contact points 22 and 28 so' that the ignition system may now be operated conventionally withouttlie transistors being introduced into the circuit.

-1; In an ignition system for an internal combustion engine having spark plugs for igniting the combustible mixture'a'nd distributor points for breaking a circuit syn- It is then electrical power, an iguition'transformer having a low tension and a hightension winding, said high-tension winding being connectible to said spark plugs, a plurality of transistors having base, collector and emitter electrodes connected in series relation so that the emitter electrode 'of one is connected to the collector electrode of the adjacent transistor and current flows through the transistors in series, said series group'being connected to said source of electrical power and to the low tension winding so that the transistors each and incombination, control the current flow through the low tension winding, a control transformer having a primary and a plurality of secondary windings inductively coupled to said primary winding, each secondary winding being connected across the base and emitterfelectrodes of one of the transistors, and the primary winding beingtconnected in circuit with the source of electrical power and distributor points to apply a pulsating'voltage thereto and control the flow of current through'the transistors for ignition purposes.

2. -ln an ignition system for an internalcombustion engine having spark plugs for igniting the combustible mixture and distributor points for breaking a circuit synchronizecl with engine operation'comprising a source of electrical power, antignition transformer having a low tension and thigh tension winding, said high tension I vary the current flow through the semiconductor'device,

chronized with engine operation comprising a source of ReferencesCited in the file of this patent UNITED STATES PATENTS 1,725,053 Browntet al Aug. 20, 1929 2,093,848" Randolph et a1. Sept. 21,. I937 2,203,579 Randolph June 4, 1940 2,338,906 Dansinge r Jan. 11, 1944 2,759,11l Wideroe Aug; 14, 1956 Giacoletto Mar. 17, 1959 

